Voltage control system



March 31, 1936. M. R. MILLER VOLTAGE CONTROL SYSTEM Filed Nov. 14, 1934I NV ENTOR MERTON R. MILLER ATTORNEY.

i atentcri l 'ihifnf Morton lliiller, Evanston,

snesne assignments, to Associated assig or, by Electric Lalooratories,"ind, Chicago, a corporation oi Delaware Application November i l, 1934,Serial No. 352,980

present invention relates in general to When the tube hashes over orbecomes conductive voltage control systems, and more in particular tosystems of this character which are adapted for use controlling theoutput voltage of an A. C. generator. The object may be stated. to bethe production of an improved and highly efiicient voltage controlsystem which will maintain the output voltage of a generator withinclose limits notwithstanding unusually large changes in the load.

The invention will he described more in detail hereinafter, referencebeing made to the accompanying drawing, which is a circuit diagram,showing how the invention may be used in practice.

Referring to the drawing, the reference letters AC indicate analternating current generator which is adapted to supply current to themains or bus-bars comprising conductors The field winding of thegenerator is indicated at Q. exciter E may he provided to furnish directcurrent for energizing the field winding It may be noted that thiscircuit includes the re" sistance 5. There may he a voltmeter V bridgedacross the mains 2 and 3.

reference letter G indicates a so -called glow tube, which may be of thecold cathode lied type as manufactured the Westingctric 2; ManufacturingGo. This .-ses a cathode an anode a grid id Eli. These elements enclosedglass receptacle of the well known led with neon gas a pressure oout oneone-hundredth or atmosphere.

n ne:

, assuin lg s es with a relay R. The ci t resistances '3', :17 as shownThor may be a condenser iii relay The s be conneo cathode throng, 1 acondenser The grid 22 of the glow tube I phase shifting circuitcomprising resistance a variable resistance ii, condenser it, and van--able condenser i3.

The relay B has a of normally closed contacts 'lhrough these contacts t,e resistance 1'5 is shunted around the resistancenecting leads tocontacts 5 versing key K.

Assuming now that the generator AC is run ning, delivering current tothe ins s and glow tuoe will'r'iash over once during that portion of thecycle i main 2 is positive with respect to lire con 5 pass through a rethe main the relay R operates and this relay therefore will continuouslyvibrate its armature at the same frequency as the frequency of thegenerator. the operated condition of the relay contacts are open, andresistance 5 is disconnected from in shunt of resistance The effectopening contacts it is therefore to reduce the current the field of thegenerator. Closing the contacts increases the current. Because of thelarge amount of iron in the field, the fluctuations are smoothed out andthe field strength may be regarded as having a substantially steadyvalue as determined lay the average current in the field. winding thevoltage should start to rise, t e glow tube (3 at once notices thechange and begins to flash over a little earlier in each cycle. The tubeis extinguished at the same point each time, and consequently the effectof the earlier flash over is to oroduce longer energlzations oi therelay R and longer openings of contacts it. The average field current istherefore reduced, which tends to reduce the voltage, counteracti cause,such as reduction in load, which. the voltage rise.

ii, on the other hand, the voltage sh to fall, due to an increased load,the will flash over later in each cycle gizations of relay 3 will becomehorter, increases the average field current -Jld to raise the voltage.

e value which the voltage a. usted or regulated adjusting t. shiitl gcircuit "ncluding the variable 1 -e condenser it x e shifting circuit cphase relation between the grid v voltage across the mains, and thus choperation or the glow tuoe causing it over on lower or higher anodepotentials e sired.

The purpose of the reversing lzey is to prevent the transfer of s etalbetween the contacts ifiiese contacts be protected by a condenser, asshown in the drawing, which reduces the sp ing to a small amount; butthe revere desirable nevertheless to insure a c iustzn nt long life ofthe contacts. re hey is periodically operated and released at convenientintervals, say once every day.

While i have shown and described one particular embodiment ofheinvention, it will he *nderstood that modifications may he madewithout departing from the pr nciples involved, I do ouid begin nan nottherefore wish to be limited to the precise form of the invention whichis shown, but desire to include and have protected by Letters Patent allforms and modifications thereof which come within the scope of theappended claims.

What is claimed is:

1. In a voltage control system, an alternating current generator, a.glow tube bridged across the output circuit of said generator, and meansincluding a relay in series with said tube for varying the fieldstrength of said generator.

2. In a voltage control system, an alternating current generator, erelay for producing a change assume in the field strength oi saidgenerator, a circuit over which said relay is bridged across the outputleads of the generator, whereby the relay is operated at the generatorfrequency, and means including a glow tube included in said circuit fordetermining the point in each cycle at which the relay is operated.

4. In a voltage control system, the combination, with an alternatingcurrent generator, of means for always changing the value of the fieldcurrent by a fixed amount at some point in each cycle, the current beingalwaysrestored to normal value at the same point in each cycle, andmeans controlled by voltage fluctuations for determining the point ineach cycle at which the current change takes place.

EERTON R. mm.

